The present invention relates to a fuel supply device for an internal combustion engine of a vehicle, such as an automobile, and to an internal combustion engine using such a fuel supply device; and, more particularly, the invention relates to a technology suitable for improving the start-up performance of an internal combustion engine and for reducing the amount of harmful substances, particularly HC, emitted from an internal combustion engine.
As a means for improving the start-up performance and improving the fuel consumption and for reducing harmful substances, particularly HC, produced in an internal combustion engine, it is effective to atomize the fuel injected from a fuel injector and to reduce the amount of fuel adhering on an inner surface of the intake pipe. Further, an improved stability of combustion can be attained by sufficiently atomizing the fuel spray. It is known to use an auxiliary fuel injector during starting operation of an internal combustion engine in order to provide a supply of atomized fuel spray to the internal combustion engine. A cold-start fuel control system comprising a cold-start fuel injector, a heater and an idle speed control valve (hereinafter, referred to as ISC valve) is disclosed in the specification and drawings of U.S. Pat. No. 5,482,023.
In this system, a part of the air from the ISC valve (a first air flow) is merged with fuel injected from the cold-start fuel injector. For this purpose, the opening of the air flow passage from the ISC valve is arranged to have an annular shape so as to surround an outlet portion of the cold-start fuel injector. The fuel from the cold-start fuel injector, just after merging with the first air flow, will enter into a cylindrical heater arranged downstream of the cold-start fuel injector.
On the other hand, an air passage for allowing part of the air from the ISC valve to flow therethrough is formed in an outer periphery of the heater, and the air flowing through this air passage (a second air flow) merges with the fuel spray that has passed through the inside of the heater at the outlet portion of the heater. The atomization of the fuel coming out from the cold-start fuel injector is promoted so that the fuel is vaporized while passing through the inside of the heater, and atomization is further promoted as the fuel is vaporized by being mixed with the second air flow at the outlet portion of the heater.
In the conventional system, a mixing chamber for mixing the fuel and the air inside a cylindrical heater is provided to form a kind of atomizer having a heater outlet as the fuel outlet. In the cold-start fuel injector, the merging point of the fuel injected from the cold-start fuel injector with the air flow and the mixing chamber constructed inside the heater are arranged in a row from the upstream side. It can be considered that the atomizer is an air assist type atomizer, which uses the energy of the air flow, and is also an internal mixing type atomizer, which performs air-liquid mixing by merging the fuel with the air inside the atomizer.
In the above-described system, the fuel spray is always in contact with the inner wall surface of the mixing chamber, that is, the inner wall surface of the heater, while the fuel is being injected. Therefore, the burden on the heater of atomizing the fuel spray becomes large and the consumed electric power also becomes large.
An object of the present invention is to provide a fuel supply device and an internal combustion engine mounting such a fuel supply device, in which it is possible to reduce the electric energy consumed in the heater in order to promote atomization of a fuel spray injected from a liquid fuel injector, or to eliminate the heater in some cases.
Another object of the present invention is to provide a fuel supply device and an internal combustion engine mounting such a fuel supply device, in which it is possible to improve the reliability and the durability of a heater by reducing the electric energy consumed by the heater.
According to the present invention, a fuel supply device comprises a fuel atomizing device for atomizing fuel into a spray injected from a liquid fuel injector by the action of a gas, the atomized fuel spray being supplied downstream of a throttle valve in an intake pipe in which the throttle valve is mounted, wherein the fuel supply device comprises a first gas passage for jetting atomizing gas which acts on the fuel spray injected from a liquid fuel injection hole of the fuel injector to promote atomization of the fuel spray, the first gas passage being opened around the liquid fuel injection hole; a second gas passage for generating a mixed gas by jetting a carrying gas to the fuel spray so as to surround the fuel spray in which atomization is promoted by the atomizing gas; and a heater disposed so as to be positioned in the periphery of a passage carrying the mixed gas.
By doing so, since the atomizing gas promotes atomization of the fuel spray and the atomization-promoted fuel spray is carried so as to be surrounded by the carrying gas, the burden of the heater is reduced and the amount of fuel adhering on the wall surface is reduced.